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/*! normalize.css v2.1.2 | MIT License | git.io/normalize */
/* ========================================================================== HTML5 display definitions ========================================================================== */
/** Correct `block` display not defined in IE 8/9. */
article, aside, details, figcaption, figure, footer, header, hgroup, main, nav, section, summary { display: block; }

/** Correct `inline-block` display not defined in IE 8/9. */
audio, canvas, video { display: inline-block; }

/** Prevent modern browsers from displaying `audio` without controls. Remove excess height in iOS 5 devices. */
audio:not([controls]) { display: none; height: 0; }

/** Address `[hidden]` styling not present in IE 8/9. Hide the `template` element in IE, Safari, and Firefox < 22. */
[hidden], template { display: none; }

script { display: none !important; }

/* ========================================================================== Base ========================================================================== */
/** 1. Set default font family to sans-serif. 2. Prevent iOS text size adjust after orientation change, without disabling user zoom. */
html { font-family: sans-serif; /* 1 */ -ms-text-size-adjust: 100%; /* 2 */ -webkit-text-size-adjust: 100%; /* 2 */ }

/** Remove default margin. */
body { margin: 0; }

/* ========================================================================== Links ========================================================================== */
/** Remove the gray background color from active links in IE 10. */
a { background: transparent; }

/** Address `outline` inconsistency between Chrome and other browsers. */
a:focus { outline: thin dotted; }

/** Improve readability when focused and also mouse hovered in all browsers. */
a:active, a:hover { outline: 0; }

/* ========================================================================== Typography ========================================================================== */
/** Address variable `h1` font-size and margin within `section` and `article` contexts in Firefox 4+, Safari 5, and Chrome. */
h1 { font-size: 2em; margin: 0.67em 0; }

/** Address styling not present in IE 8/9, Safari 5, and Chrome. */
abbr[title] { border-bottom: 1px dotted; }

/** Address style set to `bolder` in Firefox 4+, Safari 5, and Chrome. */
b, strong { font-weight: bold; }

/** Address styling not present in Safari 5 and Chrome. */
dfn { font-style: italic; }

/** Address differences between Firefox and other browsers. */
hr { -moz-box-sizing: content-box; box-sizing: content-box; height: 0; }

/** Address styling not present in IE 8/9. */
mark { background: #ff0; color: #000; }

/** Correct font family set oddly in Safari 5 and Chrome. */
code, kbd, pre, samp { font-family: monospace, serif; font-size: 1em; }

/** Improve readability of pre-formatted text in all browsers. */
pre { white-space: pre-wrap; }

/** Set consistent quote types. */
q { quotes: "\201C" "\201D" "\2018" "\2019"; }

/** Address inconsistent and variable font size in all browsers. */
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/** Prevent `sub` and `sup` affecting `line-height` in all browsers. */
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/* ========================================================================== Embedded content ========================================================================== */
/** Remove border when inside `a` element in IE 8/9. */
img { border: 0; }

/** Correct overflow displayed oddly in IE 9. */
svg:not(:root) { overflow: hidden; }

/* ========================================================================== Figures ========================================================================== */
/** Address margin not present in IE 8/9 and Safari 5. */
figure { margin: 0; }

/* ========================================================================== Forms ========================================================================== */
/** Define consistent border, margin, and padding. */
fieldset { border: 1px solid #c0c0c0; margin: 0 2px; padding: 0.35em 0.625em 0.75em; }

/** 1. Correct `color` not being inherited in IE 8/9. 2. Remove padding so people aren't caught out if they zero out fieldsets. */
legend { border: 0; /* 1 */ padding: 0; /* 2 */ }

/** 1. Correct font family not being inherited in all browsers. 2. Correct font size not being inherited in all browsers. 3. Address margins set differently in Firefox 4+, Safari 5, and Chrome. */
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/** Address Firefox 4+ setting `line-height` on `input` using `!important` in the UA stylesheet. */
button, input { line-height: normal; }

/** Address inconsistent `text-transform` inheritance for `button` and `select`. All other form control elements do not inherit `text-transform` values. Correct `button` style inheritance in Chrome, Safari 5+, and IE 8+. Correct `select` style inheritance in Firefox 4+ and Opera. */
button, select { text-transform: none; }

/** 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio` and `video` controls. 2. Correct inability to style clickable `input` types in iOS. 3. Improve usability and consistency of cursor style between image-type `input` and others. */
button, html input[type="button"], input[type="reset"], input[type="submit"] { -webkit-appearance: button; /* 2 */ cursor: pointer; /* 3 */ }

/** Re-set default cursor for disabled elements. */
button[disabled], html input[disabled] { cursor: default; }

/** 1. Address box sizing set to `content-box` in IE 8/9. 2. Remove excess padding in IE 8/9. */
input[type="checkbox"], input[type="radio"] { box-sizing: border-box; /* 1 */ padding: 0; /* 2 */ }

/** 1. Address `appearance` set to `searchfield` in Safari 5 and Chrome. 2. Address `box-sizing` set to `border-box` in Safari 5 and Chrome (include `-moz` to future-proof). */
input[type="search"] { -webkit-appearance: textfield; /* 1 */ -moz-box-sizing: content-box; -webkit-box-sizing: content-box; /* 2 */ box-sizing: content-box; }

/** Remove inner padding and search cancel button in Safari 5 and Chrome on OS X. */
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/** Remove inner padding and border in Firefox 4+. */
button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; }

/** 1. Remove default vertical scrollbar in IE 8/9. 2. Improve readability and alignment in all browsers. */
textarea { overflow: auto; /* 1 */ vertical-align: top; /* 2 */ }

/* ========================================================================== Tables ========================================================================== */
/** Remove most spacing between table cells. */
table { border-collapse: collapse; border-spacing: 0; }

meta.foundation-mq-small { font-family: "only screen and (min-width: 768px)"; width: 768px; }

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body { background: white; color: #222222; padding: 0; margin: 0; font-family: "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif; font-weight: normal; font-style: normal; line-height: 1; position: relative; cursor: auto; }

a:hover { cursor: pointer; }

img, object, embed { max-width: 100%; height: auto; }

object, embed { height: 100%; }

img { -ms-interpolation-mode: bicubic; }

#map_canvas img, #map_canvas embed, #map_canvas object, .map_canvas img, .map_canvas embed, .map_canvas object { max-width: none !important; }

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.text-left { text-align: left !important; }

.text-right { text-align: right !important; }

.text-center { text-align: center !important; }

.text-justify { text-align: justify !important; }

.hide { display: none; }

.antialiased { -webkit-font-smoothing: antialiased; }

img { display: inline-block; vertical-align: middle; }

textarea { height: auto; min-height: 50px; }

select { width: 100%; }

object, svg { display: inline-block; vertical-align: middle; }

.center { margin-left: auto; margin-right: auto; }

.spread { width: 100%; }

p.lead, .paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { font-size: 1.21875em; line-height: 1.6; }

.subheader, .admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { line-height: 1.4; color: black; font-weight: 300; margin-top: 0.2em; margin-bottom: 0.5em; }

/* Typography resets */
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/* Default Link Styles */
a { color: #0068b0; text-decoration: none; line-height: inherit; }
a:hover, a:focus { color: #333333; }
a img { border: none; }

/* Default paragraph styles */
p { font-family: Noto, sans-serif; font-weight: normal; font-size: 1em; line-height: 1.6; margin-bottom: 0.75em; text-rendering: optimizeLegibility; }
p aside { font-size: 0.875em; line-height: 1.35; font-style: italic; }

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h1 small, h2 small, h3 small, #toctitle small, .sidebarblock > .content > .title small, h4 small, h5 small, h6 small { font-size: 60%; color: #4d4d4d; line-height: 0; }

h1 { font-size: 2.125em; }

h2 { font-size: 1.6875em; }

h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.375em; }

h4 { font-size: 1.125em; }

h5 { font-size: 1.125em; }

h6 { font-size: 1em; }

hr { border: solid #dddddd; border-width: 1px 0 0; clear: both; margin: 1.25em 0 1.1875em; height: 0; }

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em, i { font-style: italic; line-height: inherit; }

strong, b { font-weight: bold; line-height: inherit; }

small { font-size: 60%; line-height: inherit; }

code { font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; color: #264357; }

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ul, ol { margin-left: 1.5em; }
ul.no-bullet, ol.no-bullet { margin-left: 1.5em; }

/* Unordered Lists */
ul li ul, ul li ol { margin-left: 1.25em; margin-bottom: 0; font-size: 1em; /* Override nested font-size change */ }
ul.square li ul, ul.circle li ul, ul.disc li ul { list-style: inherit; }
ul.square { list-style-type: square; }
ul.circle { list-style-type: circle; }
ul.disc { list-style-type: disc; }
ul.no-bullet { list-style: none; }

/* Ordered Lists */
ol li ul, ol li ol { margin-left: 1.25em; margin-bottom: 0; }

/* Definition Lists */
dl dt { margin-bottom: 0.3em; font-weight: bold; }
dl dd { margin-bottom: 0.75em; }

/* Abbreviations */
abbr, acronym { text-transform: uppercase; font-size: 90%; color: black; border-bottom: 1px dotted #dddddd; cursor: help; }

abbr { text-transform: none; }

/* Blockquotes */
blockquote { margin: 0 0 0.75em; padding: 0.5625em 1.25em 0 1.1875em; border-left: 1px solid #dddddd; }
blockquote cite { display: block; font-size: 0.8125em; color: #5e93b8; }
blockquote cite:before { content: "\2014 \0020"; }
blockquote cite a, blockquote cite a:visited { color: #5e93b8; }

blockquote, blockquote p { line-height: 1.6; color: #333333; }

/* Microformats */
.vcard { display: inline-block; margin: 0 0 1.25em 0; border: 1px solid #dddddd; padding: 0.625em 0.75em; }
.vcard li { margin: 0; display: block; }
.vcard .fn { font-weight: bold; font-size: 0.9375em; }

.vevent .summary { font-weight: bold; }
.vevent abbr { cursor: auto; text-decoration: none; font-weight: bold; border: none; padding: 0 0.0625em; }

@media only screen and (min-width: 768px) { h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }
  h1 { font-size: 2.75em; }
  h2 { font-size: 2.3125em; }
  h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.6875em; }
  h4 { font-size: 1.4375em; } }
/* Tables */
table { background: white; margin-bottom: 1.25em; border: solid 1px #d8d8ce; }
table thead, table tfoot { background: -webkit-linear-gradient(top, #add386, #90b66a); font-weight: bold; }
table thead tr th, table thead tr td, table tfoot tr th, table tfoot tr td { padding: 0.5em 0.625em 0.625em; font-size: inherit; color: white; text-align: left; }
table tr th, table tr td { padding: 0.5625em 0.625em; font-size: inherit; color: #6d6e71; }
table tr.even, table tr.alt, table tr:nth-of-type(even) { background: #edf2f2; }
table thead tr th, table tfoot tr th, table tbody tr td, table tr td, table tfoot tr td { display: table-cell; line-height: 1.4; }

body { -moz-osx-font-smoothing: grayscale; -webkit-font-smoothing: antialiased; tab-size: 4; }

h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }

a:hover, a:focus { text-decoration: underline; }

.clearfix:before, .clearfix:after, .float-group:before, .float-group:after { content: " "; display: table; }
.clearfix:after, .float-group:after { clear: both; }

*:not(pre) > code { font-size: inherit; font-style: normal !important; letter-spacing: 0; padding: 0; background-color: white; -webkit-border-radius: 0; border-radius: 0; line-height: inherit; word-wrap: break-word; }
*:not(pre) > code.nobreak { word-wrap: normal; }
*:not(pre) > code.nowrap { white-space: nowrap; }

pre, pre > code { line-height: 1.6; color: #264357; font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: normal; }

em em { font-style: normal; }

strong strong { font-weight: normal; }

.keyseq { color: #333333; }

kbd { font-family: Consolas, "Liberation Mono", Courier, monospace; display: inline-block; color: black; font-size: 0.65em; line-height: 1.45; background-color: #f7f7f7; border: 1px solid #ccc; -webkit-border-radius: 3px; border-radius: 3px; -webkit-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; margin: 0 0.15em; padding: 0.2em 0.5em; vertical-align: middle; position: relative; top: -0.1em; white-space: nowrap; }

.keyseq kbd:first-child { margin-left: 0; }

.keyseq kbd:last-child { margin-right: 0; }

.menuseq, .menuref { color: #000; }

.menuseq b:not(.caret), .menuref { font-weight: inherit; }

.menuseq { word-spacing: -0.02em; }
.menuseq b.caret { font-size: 1.25em; line-height: 0.8; }
.menuseq i.caret { font-weight: bold; text-align: center; width: 0.45em; }

b.button:before, b.button:after { position: relative; top: -1px; font-weight: normal; }

b.button:before { content: "["; padding: 0 3px 0 2px; }

b.button:after { content: "]"; padding: 0 2px 0 3px; }

#header, #content, #footnotes, #footer { width: 100%; margin-left: auto; margin-right: auto; margin-top: 0; margin-bottom: 0; max-width: 62.5em; *zoom: 1; position: relative; padding-left: 1.5em; padding-right: 1.5em; }
#header:before, #header:after, #content:before, #content:after, #footnotes:before, #footnotes:after, #footer:before, #footer:after { content: " "; display: table; }
#header:after, #content:after, #footnotes:after, #footer:after { clear: both; }

#content { margin-top: 1.25em; }

#content:before { content: none; }

#header > h1:first-child { color: black; margin-top: 2.25rem; margin-bottom: 0; }
#header > h1:first-child + #toc { margin-top: 8px; border-top: 1px solid #dddddd; }
#header > h1:only-child, body.toc2 #header > h1:nth-last-child(2) { border-bottom: 1px solid #dddddd; padding-bottom: 8px; }
#header .details { border-bottom: 1px solid #dddddd; line-height: 1.45; padding-top: 0.25em; padding-bottom: 0.25em; padding-left: 0.25em; color: #5e93b8; display: -ms-flexbox; display: -webkit-flex; display: flex; -ms-flex-flow: row wrap; -webkit-flex-flow: row wrap; flex-flow: row wrap; }
#header .details span:first-child { margin-left: -0.125em; }
#header .details span.email a { color: #333333; }
#header .details br { display: none; }
#header .details br + span:before { content: "\00a0\2013\00a0"; }
#header .details br + span.author:before { content: "\00a0\22c5\00a0"; color: #333333; }
#header .details br + span#revremark:before { content: "\00a0|\00a0"; }
#header #revnumber { text-transform: capitalize; }
#header #revnumber:after { content: "\00a0"; }

#content > h1:first-child:not([class]) { color: black; border-bottom: 1px solid #dddddd; padding-bottom: 8px; margin-top: 0; padding-top: 1rem; margin-bottom: 1.25rem; }

#toc { border-bottom: 0 solid #dddddd; padding-bottom: 0.5em; }
#toc > ul { margin-left: 0.125em; }
#toc ul.sectlevel0 > li > a { font-style: italic; }
#toc ul.sectlevel0 ul.sectlevel1 { margin: 0.5em 0; }
#toc ul { font-family: Noto, sans-serif; list-style-type: none; }
#toc li { line-height: 1.3334; margin-top: 0.3334em; }
#toc a { text-decoration: none; }
#toc a:active { text-decoration: underline; }

#toctitle { color: black; font-size: 1.2em; }

@media only screen and (min-width: 768px) { #toctitle { font-size: 1.375em; }
  body.toc2 { padding-left: 15em; padding-right: 0; }
  #toc.toc2 { margin-top: 0 !important; background-color: white; position: fixed; width: 15em; left: 0; top: 0; border-right: 1px solid #dddddd; border-top-width: 0 !important; border-bottom-width: 0 !important; z-index: 1000; padding: 1.25em 1em; height: 100%; overflow: auto; }
  #toc.toc2 #toctitle { margin-top: 0; margin-bottom: 0.8rem; font-size: 1.2em; }
  #toc.toc2 > ul { font-size: 0.9em; margin-bottom: 0; }
  #toc.toc2 ul ul { margin-left: 0; padding-left: 1em; }
  #toc.toc2 ul.sectlevel0 ul.sectlevel1 { padding-left: 0; margin-top: 0.5em; margin-bottom: 0.5em; }
  body.toc2.toc-right { padding-left: 0; padding-right: 15em; }
  body.toc2.toc-right #toc.toc2 { border-right-width: 0; border-left: 1px solid #dddddd; left: auto; right: 0; } }
@media only screen and (min-width: 1280px) { body.toc2 { padding-left: 20em; padding-right: 0; }
  #toc.toc2 { width: 20em; }
  #toc.toc2 #toctitle { font-size: 1.375em; }
  #toc.toc2 > ul { font-size: 0.95em; }
  #toc.toc2 ul ul { padding-left: 1.25em; }
  body.toc2.toc-right { padding-left: 0; padding-right: 20em; } }
#content #toc { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
#content #toc > :first-child { margin-top: 0; }
#content #toc > :last-child { margin-bottom: 0; }

#footer { max-width: 100%; background-color: none; padding: 1.25em; }

#footer-text { color: black; line-height: 1.44; }

#content { margin-bottom: 0.625em; }

.sect1 { padding-bottom: 0.625em; }

@media only screen and (min-width: 768px) { #content { margin-bottom: 1.25em; }
  .sect1 { padding-bottom: 1.25em; } }
.sect1:last-child { padding-bottom: 0; }

.sect1 + .sect1 { border-top: 0 solid #dddddd; }

#content h1 > a.anchor, h2 > a.anchor, h3 > a.anchor, #toctitle > a.anchor, .sidebarblock > .content > .title > a.anchor, h4 > a.anchor, h5 > a.anchor, h6 > a.anchor { position: absolute; z-index: 1001; width: 1.5ex; margin-left: -1.5ex; display: block; text-decoration: none !important; visibility: hidden; text-align: center; font-weight: normal; }
#content h1 > a.anchor:before, h2 > a.anchor:before, h3 > a.anchor:before, #toctitle > a.anchor:before, .sidebarblock > .content > .title > a.anchor:before, h4 > a.anchor:before, h5 > a.anchor:before, h6 > a.anchor:before { content: "\00A7"; font-size: 0.85em; display: block; padding-top: 0.1em; }
#content h1:hover > a.anchor, #content h1 > a.anchor:hover, h2:hover > a.anchor, h2 > a.anchor:hover, h3:hover > a.anchor, #toctitle:hover > a.anchor, .sidebarblock > .content > .title:hover > a.anchor, h3 > a.anchor:hover, #toctitle > a.anchor:hover, .sidebarblock > .content > .title > a.anchor:hover, h4:hover > a.anchor, h4 > a.anchor:hover, h5:hover > a.anchor, h5 > a.anchor:hover, h6:hover > a.anchor, h6 > a.anchor:hover { visibility: visible; }
#content h1 > a.link, h2 > a.link, h3 > a.link, #toctitle > a.link, .sidebarblock > .content > .title > a.link, h4 > a.link, h5 > a.link, h6 > a.link { color: black; text-decoration: none; }
#content h1 > a.link:hover, h2 > a.link:hover, h3 > a.link:hover, #toctitle > a.link:hover, .sidebarblock > .content > .title > a.link:hover, h4 > a.link:hover, h5 > a.link:hover, h6 > a.link:hover { color: black; }

.audioblock, .imageblock, .literalblock, .listingblock, .stemblock, .videoblock { margin-bottom: 1.25em; }

.admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { text-rendering: optimizeLegibility; text-align: left; }

table.tableblock > caption.title { white-space: nowrap; overflow: visible; max-width: 0; }

.paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { color: black; }

table.tableblock #preamble > .sectionbody > .paragraph:first-of-type p { font-size: inherit; }

.admonitionblock > table { border-collapse: separate; border: 0; background: none; width: 100%; }
.admonitionblock > table td.icon { text-align: center; width: 80px; }
.admonitionblock > table td.icon img { max-width: initial; }
.admonitionblock > table td.icon .title { font-weight: bold; font-family: Noto, sans-serif; text-transform: uppercase; }
.admonitionblock > table td.content { padding-left: 1.125em; padding-right: 1.25em; border-left: 1px solid #dddddd; color: #5e93b8; }
.admonitionblock > table td.content > :last-child > :last-child { margin-bottom: 0; }

.exampleblock > .content { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
.exampleblock > .content > :first-child { margin-top: 0; }
.exampleblock > .content > :last-child { margin-bottom: 0; }

.sidebarblock { border-style: solid; border-width: 1px; border-color: #e6e6e6; margin-bottom: 1.25em; padding: 1.25em; background: white; -webkit-border-radius: 0; border-radius: 0; }
.sidebarblock > :first-child { margin-top: 0; }
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<body class="book">
<div id="header">
<h1>cl_intel_spirv_subgroups</h1>
<div class="details">
<span id="revnumber">version V2.2-11-30-g5ba09e4,</span>
<span id="revdate">Thu, 24 Oct 2019 22:38:27 +0000</span>
<br><span id="revremark">from git branch: public_master commit: 5ba09e43bb29a2292d6af0b70148a9f846e1806f</span>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_name_strings">Name Strings</h2>
<div class="sectionbody">
<div class="paragraph">
<p><code>cl_intel_spirv_subgroups</code></p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_contact">Contact</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Ben Ashbaugh, Intel (ben 'dot' ashbaugh 'at' intel 'dot' com)</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_contributors">Contributors</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Ben Ashbaugh, Intel<br>
Biju George, Intel<br>
Michael Kinsner, Intel<br>
Mariusz Merecki, Intel</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_notice">Notice</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Copyright (c) 2018-2019 Intel Corporation.  All rights reserved.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_status">Status</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Final Draft</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_version">Version</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Built On: 2019-10-23<br>
Revision: 2</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_dependencies">Dependencies</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This extension is written against the OpenCL SPIR-V Environment Specification Version 2.2, Revision v2.2-3.</p>
</div>
<div class="paragraph">
<p>This extension requires OpenCL support for SPIR-V, either via OpenCL 2.1 or via the <code>cl_khr_il_program</code> extension, and support for the <code>cl_intel_subgroups</code> extension.</p>
</div>
<div class="paragraph">
<p>This extension interacts with the <code>cl_intel_subgroups_short</code> extension.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_overview">Overview</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This extension defines how modules using the SPIR-V extension <code>SPV_INTEL_subgroups</code> may behave in an OpenCL environment.</p>
</div>
<div class="paragraph">
<p>This extension is a companion to the <code>cl_intel_subgroups</code> and <code>cl_intel_subgroups_short</code> OpenCL extensions, and the functionality described in this extension and <code>SPV_INTEL_subgroups</code> is sufficient to implement the built-in functions defined in the <code>cl_intel_subgroups</code> and <code>cl_intel_subgroups_short</code> extensions.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_new_api_functions">New API Functions</h2>
<div class="sectionbody">
<div class="paragraph">
<p>None.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_new_api_enums">New API Enums</h2>
<div class="sectionbody">
<div class="paragraph">
<p>None.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_modifications_to_the_opencl_spir_v_environment_specification">Modifications to the OpenCL SPIR-V Environment Specification</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_add_a_new_section_7_1_x_cl_intel_spirv_subgroups">Add a new Section 7.1.X - <code>cl_intel_spirv_subgroups</code></h3>
<div class="paragraph">
<p>If the OpenCL environment supports the extension <code>cl_intel_spirv_subgroups</code>, then the environment must accept SPIR-V modules that declare use of the <code>SPV_INTEL_subgroups</code> extension via <strong>OpExtension</strong>.</p>
</div>
<div class="paragraph">
<p>If the OpenCL environment supports the extension <code>cl_intel_spirv_subgroups</code> and use of the <code>SPV_INTEL_subgroups</code> extension is declared in the module via <strong>OpExtension</strong>, then the environment must accept modules that declare the following SPIR-V capabilities:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>SubgroupShuffleINTEL</strong></p>
</li>
<li>
<p><strong>SubgroupBufferBlockIOINTEL</strong></p>
</li>
<li>
<p><strong>SubgroupImageBlockIOINTEL</strong></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, the environment must accept modules that use the following <strong>BuiltIns</strong>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>SubgroupSize</strong></p>
</li>
<li>
<p><strong>SubgroupMaxSize</strong></p>
</li>
<li>
<p><strong>NumSubgroups</strong></p>
</li>
<li>
<p><strong>SubgroupId</strong></p>
</li>
<li>
<p><strong>SubgroupLocalInvocationId</strong></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>For an OpenCL 2.0 or newer environment, the following <strong>BuiltIns</strong> must additionally be accepted:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>NumEnqueuedSubgroups</strong></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, the environment must accept the following instruction semantics:</p>
</div>
<div class="paragraph">
<p>For the control <em>Barrier Instruction</em>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>OpControlBarrier</strong>:</p>
<div class="ulist">
<ul>
<li>
<p>The <em>Scope</em> for <em>Execution</em> may be <strong>Subgroup</strong>.</p>
</li>
<li>
<p>The <em>Scope</em> for <em>Memory</em> may be <strong>Subgroup</strong>.</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<div class="paragraph">
<p>For the <em>Group Instructions</em>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>OpGroupAll</strong></p>
</li>
<li>
<p><strong>OpGroupAny</strong></p>
</li>
<li>
<p><strong>OpGroupBroadcast</strong></p>
</li>
<li>
<p><strong>OpGroupIAdd</strong></p>
</li>
<li>
<p><strong>OpGroupFAdd</strong></p>
</li>
<li>
<p><strong>OpGroupFMin</strong></p>
</li>
<li>
<p><strong>OpGroupUMin</strong></p>
</li>
<li>
<p><strong>OpGroupSMin</strong></p>
</li>
<li>
<p><strong>OpGroupFMax</strong></p>
</li>
<li>
<p><strong>OpGroupUMax</strong></p>
</li>
<li>
<p><strong>OpGroupSMax</strong></p>
<div class="ulist">
<ul>
<li>
<p>The <em>Scope</em> for <em>Execution</em> may be <strong>Subgroup</strong>.</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</div>
<div class="sect2">
<h3 id="_add_a_new_section_7_1_x_1_shuffle_instructions">Add a new Section 7.1.X.1 - Shuffle Instructions</h3>
<div class="paragraph">
<p>Because support for <code>cl_intel_subgroups</code> is required for <code>cl_intel_spirv_subgroups</code>, if the OpenCL environment supports the extension <code>cl_intel_spirv_subgroups</code> and use of the <code>SPV_INTEL_subgroups</code> extension is declared in the module via <strong>OpExtension</strong>, then the environment must accept the following types for 'Data' for the <strong>SubgroupShuffleINTEL</strong> instructions:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars and <strong>OpTypeVectors</strong> with 2, 3, 4, 8, or 16 <em>Component Count</em> components of the following <em>Component Type</em> types:</p>
<div class="ulist">
<ul>
<li>
<p><strong>OpTypeFloat</strong> with a <em>Width</em> of 32 bits (equivalent to <code>float</code>)</p>
</li>
<li>
<p><strong>OpTypeInt</strong> with a <em>Width</em> of 32 bits and <em>Signedness</em> of 0 (equivalent to <code>int</code> and <code>uint</code>)</p>
</li>
</ul>
</div>
</li>
<li>
<p>Scalars of <strong>OpTypeInt</strong> with a <em>Width</em> of 64 bits and <em>Signedness</em> of 0 (equivalent to <code>long</code> and <code>ulong</code>)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, if the <strong>Float16</strong> capability is declared and supported:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars of <strong>OpTypeFloat</strong> with a <em>Width</em> of 16 bits (equivalent to <code>half</code>)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, if the <strong>Float64</strong> capability is declared and supported:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars of <strong>OpTypeFloat</strong> with a <em>Width</em> of 64 bits (equivalent to <code>double</code>)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, if the OpenCL environment supports the extension <code>cl_intel_subgroups_short</code>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars and <strong>OpTypeVectors</strong> with 2, 3, 4, 8, or 16 <em>Component Count</em> components of the following <em>Component Type</em> types:</p>
<div class="ulist">
<ul>
<li>
<p><strong>OpTypeInt</strong> with a <em>Width</em> of 16 bits and <em>Signedness</em> of 0 (equivalent to <code>short</code> and <code>ushort</code>)</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
</div>
<div class="sect2">
<h3 id="_add_a_new_section_7_1_x_2_block_io_instructions">Add a new Section 7.1.X.2 - Block IO Instructions</h3>
<div class="paragraph">
<p>Because support for <code>cl_intel_subgroups</code> is required for <code>cl_intel_spirv_subgroups</code>, if the OpenCL environment supports the extension <code>cl_intel_spirv_subgroups</code> and use of the <code>SPV_INTEL_subgroups</code> extension is declared in the module via <strong>OpExtension</strong>, then the environment must accept the following types for <em>Result</em> and <em>Data</em> for the <strong>SubgroupBufferBlockIOINTEL</strong> and <strong>SubgroupImageBlockIOINTEL</strong> instructions:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars and <strong>OpTypeVectors</strong> with 2, 4, or 8 <em>Component Count</em> components of the following <em>Component Type</em> types:</p>
<div class="ulist">
<ul>
<li>
<p><strong>OpTypeInt</strong> with a <em>Width</em> of 32 bits and <em>Signedness</em> of 0 (equivalent to <code>int</code> and <code>uint</code>)</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<div class="paragraph">
<p>Additionally, if the OpenCL environment supports the extension <code>cl_intel_subgroups_short</code>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Scalars and <strong>OpTypeVectors</strong> with 2, 4, or 8 <em>Component Count</em> components of the following <em>Component Type</em> types:</p>
<div class="ulist">
<ul>
<li>
<p><strong>OpTypeInt</strong> with a <em>Width</em> of 16 bits and <em>Signedness</em> of 0 (equivalent to <code>short</code> and <code>ushort</code>)</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<div class="paragraph">
<p>For <em>Ptr</em>, valid <em>Storage Classes</em> are:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>CrossWorkGroup</strong> (equivalent to the <code>global</code> address space)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>For <em>Image</em>:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><em>Dim</em> must be <strong>2D</strong></p>
</li>
<li>
<p><em>Depth</em> must be 0 (not a depth image)</p>
</li>
<li>
<p><em>Arrayed</em> must be 0 (non-arrayed content)</p>
</li>
<li>
<p><em>MS</em> must be 0 (single-sampled content)</p>
</li>
<li>
<p>(equivalent to <code>image2d_t</code>)</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>For <em>Coordinate</em>, the following types are supported:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><strong>OpTypeVectors</strong> with 2 <em>Component Count</em> components of <em>Component Type</em> <strong>OpTypeInt</strong> with a <em>Width</em> of 32 bits and <em>Signedness</em> of 0 (equivalent to <code>int2</code>)</p>
</li>
</ul>
</div>
</div>
<div class="sect2">
<h3 id="_add_a_new_section_7_1_x_3_notes_and_restrictions">Add a new Section 7.1.X.3 - Notes and Restrictions</h3>
<div class="paragraph">
<p>The <strong>SubgroupShuffleINTEL</strong> instructions may be placed within non-uniform control flow and hence do not have to be encountered by all invocations in the subgroup, however <em>Data</em> may only be shuffled among invocations encountering the <strong>SubgroupShuffleINTEL</strong> instruction.  Shuffling <em>Data</em> from an invocation that does not encounter the <strong>SubgroupShuffleINTEL</strong> instruction will produce undefined results.</p>
</div>
<div class="paragraph">
<p>There is no defined behavior for out-of-range shuffle indices for the <strong>SubgroupShuffleINTEL</strong> instructions.</p>
</div>
<div class="paragraph">
<p>The <strong>SubgroupBufferBlockIOINTEL</strong> and <strong>SubgroupImageBlockIOINTEL</strong> instructions are only guaranteed to work correctly if placed strictly within uniform control flow within the subgroup.  This ensures that if any invocation executes it, all invocations will execute it.  If placed elsewhere, behavior is undefined.</p>
</div>
<div class="paragraph">
<p>There is no defined out-of-range behavior for the <strong>SubgroupBufferBlockIOINTEL</strong> instructions.</p>
</div>
<div class="paragraph">
<p>The <strong>SubgroupImageBlockIOINTEL</strong> instructions do support bounds checking, however they bounds-check to the image width in units of <code>uints</code>, not in units of image elements.  This means:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>If the image has an <em>Image Format</em> size equal to the size of a <code>uint</code> (four bytes, for example <strong>Rgba8</strong>), the image will be correctly bounds-checked.  In this case, out-of-bounds reads will return the edge image element (the equivalent of <strong>ClampToEdge</strong>), and out-of-bounds writes will be ignored.</p>
</li>
<li>
<p>If the image has an <em>Image Format</em> size less than the size of a <code>uint</code> (such as <strong>R8</strong>), the entire image is addressable, however bounds checking will occur too late.  For this reason, extra care should be taken to avoid out-of-bounds reads and writes, since out-of-bounds reads may return invalid data and out-of-bounds writes may corrupt other images or buffers unpredictably.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The following restrictions apply to the <strong>SubgroupBufferBlockIOINTEL</strong> instructions:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>The pointer <em>Ptr</em> must be 32-bit (4-byte) aligned for reads, and must be 128-bit (16-byte) aligned for writes.</p>
</li>
<li>
<p>If the pointer <em>Ptr</em> is computed from a kernel argument that is a <code>cl_mem</code> that was created with <code>CL_MEM_USE_HOST_PTR</code>, then the <em>host_ptr</em> must be 32-bit (4-byte) aligned for reads, and must be 128-bit (16-byte) aligned for writes.</p>
</li>
<li>
<p>If the pointer <em>Ptr</em> is computed from a kernel argument that is a <code>cl_mem</code> that is a sub-buffer, then the <em>origin</em> defining the sub-buffer offset into the <em>buffer</em> must be a multiple of 4 bytes for reads, and must be a multiple of 16 bytes for write, in addition to the <code>CL_DEVICE_MEM_BASE_ADDR_ALIGN</code> requirements.  Additionally, if the <em>buffer</em> that the sub-buffer is created from was created with <code>CL_MEM_USE_HOST_PTR</code>, then the <em>host_ptr</em> for the <em>buffer</em> must be 32-bit (4-byte) aligned for reads, and must be 128-bit (16-byte) aligned for writes.</p>
</li>
<li>
<p>If the pointer <em>Ptr</em> is computed from an SVM pointer kernel argument, then the SVM pointer kernel argument must be 32-bit (4-byte) aligned for reads, and must be 128-bit (16-byte) aligned for writes.</p>
</li>
<li>
<p>Behavior is undefined if the <strong>SubgroupSize</strong> is smaller than <strong>SubgruopMaxSize</strong>; in other words, if this is a partial subgroup.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The following restrictions apply to the <strong>SubgroupImageBlockIOINTEL</strong> instructions:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>The behavior of the <strong>SubgroupImageBlockIOINTEL</strong> instructions is undefined for images with an element size greater than four bytes (such as <strong>Rgba32f</strong>).</p>
</li>
<li>
<p>When reading or writing a 2D image created from a buffer with the <strong>SubgroupImageBlockIOINTEL</strong> instructions, the image row pitch is required to be a multiple of 64-bytes, in addition to the <code>CL_DEVICE_IMAGE_PITCH_ALIGNMENT</code> requirements.</p>
</li>
<li>
<p>When reading or writing a 2D image created from a buffer with the <strong>SubgroupImageBlockIOINTEL</strong> instructions, if the buffer is a <code>cl_mem</code> that was created with <code>CL_MEM_USE_HOST_PTR</code>, then the <em>host_ptr</em> must be 256-bit (32-byte) aligned.</p>
</li>
<li>
<p>When reading or writing a 2D image created from a buffer with the <strong>SubgroupImageBlockIOINTEL</strong> instructions, if the buffer is a <code>cl_mem</code> that is a sub-buffer, then the <em>origin</em> must be a multiple of 32-bytes.  Additionally, if the <em>buffer</em> that the sub-buffer is created from was created with <code>CL_MEM_USE_HOST_PTR</code>, then the <em>host_ptr</em> for the <em>buffer</em> must be 256-bit (32-byte) aligned.</p>
</li>
<li>
<p>Behavior is undefined if the <strong>SubgroupSize</strong> is smaller than <strong>SubgruopMaxSize</strong>; in other words, if this is a partial subgroup.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The following restrictions apply to the <strong>OpSubgroupImageBlockWriteINTEL</strong> instruction:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Unlike the image block read instruction, which may read from any arbitrary byte offset, the x-component of the byte coordinate for the image block write instruction must be a multiple of four; in other words, the write must begin at a 32-bit boundary.  There is no restriction on the y-component of the coordinate.</p>
</li>
</ul>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_issues">Issues</h2>
<div class="sectionbody">
<div class="paragraph">
<p>None.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_revision_history">Revision History</h2>
<div class="sectionbody">
<table class="tableblock frame-all grid-rows stretch">
<colgroup>
<col style="width: 4.7619%;">
<col style="width: 14.2857%;">
<col style="width: 14.2857%;">
<col style="width: 66.6667%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Rev</th>
<th class="tableblock halign-left valign-top">Date</th>
<th class="tableblock halign-left valign-top">Author</th>
<th class="tableblock halign-left valign-top">Changes</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">1</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">2018-10-29</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Ben Ashbaugh</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>Initial revision</strong></p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">2019-09-17</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Ben Ashbaugh</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Added 3-component vector support for shuffles, restriction for block reads and writes and partial subgroups, and asciidoctor formatting fixes.</p></td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
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